More than 40 people were killed after a bus fell into a ravine and caught fire in the southern Pakistani province of Balochistan on Sunday, officials said.

Forty-one bodies had been recovered from the wreckage, some burned beyond recognition, district police officer Israr Umrani told Reuters.

The bus carrying around 48 people crashed on the way from Balochistan's capital of Quetta to the southern city of Karachi, officials said.

Dozens of people were combing through the wreckage, footage shared by the Edhi Foundation aid and emergency response organisation showed, and ambulance workers were carrying a dead body out of the debris.

Assistant Commissioner Hamza Anjum for Lasbela, a district in Balochistan, told Dawn newspaper the vehicle had crashed into a bridge, causing it to fall into a ravine and catch fire.

Fatal road accidents are common in Pakistan, where traffic rules are rarely followed and roads in many rural areas are in poor condition.

At least 22 people were killed in June, including nine members of one family when a passenger van fell into deep ravine in Balochistan.